Hydropneumatic counterbalance



Feb. 25,

H- W- RAM EY HYDROPNEUMAT I C COUNTERBALANCE `Patented Feb. 25, 1941 f' UNITED STATES i 2,233,226 nYDaorNEUMATIC coUNTEaBALANcE Harold Williams Rainey, Parkersburg, W. Va., as-

signor to The Parkersburg Rig Beel Company, Parkersburg, W. Va., a. corporation of West Virginia lApplication August 8, 1938, Serial No. 223,737

24 Claims.

This invention relates to hydropneumatic counterbalances especially adapted for use with oil well pumping rigs. j

In the copending application of Robert Griffin y De La Mater, Serial No. 157,189, flied August 3,

1937, there vis described and claimed a particularly efficient type of hydropneumatic counterbalance particularly adapted for use .with the walking beams of oil well pumping rigs. As disclosed 1,0 in such copending application, it has been the common practice to counter-weight the walking beams of oil well pumping rigs to equalize the power demand throughout the pumping cycle.

r On the down-stroke of the rods and pump plunger, the weight suspended from the well end of the walking beam is essentially the weight of the pump rods, and on an uncounterbalanced rig, this weight would pull the beam down and thus require no power for moving the beam.

On the up-stroke of the pump rods and plunger, the weight suspended from the well end of the walking beam is essentially the weight of the rods plus the weight of the fluid being lifted. With an uncounterbalanced pum-ping rig the prime mover is required to furnish all of the power necessary for lifting such total weight.

As a result it is obvious that the power cycle would be very uneven in an uncounterbalanced rig, the power varying fromnegative to positive 30 and being greatly affected by other forces such as inertia, etc.

Infcounterbalancing an oil pumping rig, it is the common practice to provide counterbalancing approximating theextent of the weight of the pump rods, plus half the weight of the fluid lifted on each up-stroke of the pump rods. Thus on the down-stroke, the weight of the counterbalance is-greaterthan the weight of the pump rods, the difference being approximately equal to onehalf the weight of the fluid lifted on each upstroke of the pump rods.y On the up-stroke the counterbalance, which was raised on the downstroke, balances of! the weight of the pump rods, plus half the weight of the liquid being lifted, and accordingly the weight required to be lifted by the prime mover and h-alf the weight of the liquid on each of the strokes of the pump rods.

Until the development of the construction disclosed in the copending application referred to, the walking beamsof oil well pumping rigs were commonly counterbalanced in either of two ways, namely, by counter-weighting the walking beam itselfy or by counter-weighting the crank shaft from which the pitman is driven. Each of these systems-possesses advantages which are offset by substantial disadvantages. For example, the theoretically ideal position for providing the counterbalancing is at the well end of the walking beam, which point is close to the point of application of loads to the walking beam. This ar- 5 rangement, however, is disadvantageous because of the great amount, of weightwhich must be mounted on the beam, the inertia of the weights at the -top and bottom of the pumping stroke being s0 great as to require a beam of substantial construction to support the loads to which it is subjected. There are further disadvantages to the counter-weighting of the walking beam which are discussed in the copending application'referred to and need not be described in detail in connection with the present invention.

Rotary crank weights have been more extensively yused with beam weights because of certain inherent advantages which they possess. For example, less damage results in case of a failure of the pitman or pump rods and it is far more convenient to handle the beam when the pitman is disconnected therefrom. Moreover, vrotary counter-weights are more readily adjustedl for lag and lead, and they always mai'x'itain''fthe'` pitman in tensionv instead of alternately ixij'tefnsion and under compression. However, rotarycrank weights are far from easily adjustable, inspite of their advantage over beam weights, substantial diilculties being encountered in handlingand adjusting the weights. It also is obvious that rotary counter-weights add substantial loads to the crank and crank shaft.

Having in mind the disadvantages inherent in weight counterbalancing, numerous efforts have been made to provide counterbalancing by pneumatic means which operates to store energy on the down stroke of the pump rods and to expend energy on the up-stroke. Such a mechanism involves numerous advantages over conventional counter-weighting in that it permitsthe application of the counterbalancing force substantially at the ideal point while eliminating the use of heavy masses of weights on the walking beam or crank shaft. Thus `the pumping equipment is more portable and more easily installed, and requires less foundation forstability.

However, pneumatic counterbalances also hav been found in practice to involve numerous disadvantages. `Such disadvantages are discussed in the copending application referred to and the construction shown therein has been highly efficient in operation with all of the inherent advantages of prior systems without any of their disadvantages. In the structure of the prior vlas application referred to, a plunger is mounted to reciprocate in a cylinder having a lower end communicating with a. receiver of substantial volume. the plunger being pivotally connected at its upper end to the walking beam, and the cylinder-receiver unit being pivotally connected at its lower end to the foundation of the rig. 'Ihe receiver is provided with a body of a non-compressible fluid such as oil which is vdisplaceable from the lower end of the cylinder on each down stroke of the plunger to compress air or other compressible gas entrapped in the receiver above the level of the oil. The quantity of the oil is variable for providing diiferent counterbalancing actions, but sumcient oil is maintained in the receiver so that the level of the oil is never below the lower end of the cylinder. Accordingly it is impossible for any of the entrapped air to enter the lower end of the cylinder to leak pa'st the plunger, and accordingly such construction provides no problem a's to air leakage.

'I'he quantity of the oil employed may be varied in accordance with the desired differential between minimum and maximum pressures in the receiver according to the particular installation, which is a result not obtainable with weight counterbalances or pneumatic counterbalances. Automatic means is provided for maintaining the desired quantity of oil in the receiver to maintain a predetermined maximum pressure therein. Such automatic means is desirable because of minor leakages of oil past the plunger, and to compensate for expansion and contraction incident to temperature changes.

'I'he automatic means referred to 'comprises a pump connected between an oil reservoir and the receiver and preferably operated by the horizontal component of movement in the receiver incident to swinging movement of the walking'beam. A`

blow oil valve is provided between the pump and the receiver to permit pumped oil to be by-passed to the reservoir instead of being passed to the receiver -so long as the maximumpressure is maintained in the latter, the blow oilr valve being adjustable to determine the blow 01T pressure. Thus a practicable counterbalancing mechanism is provided which loperates eiiiciently over long periods of time without any attention on the part of the operator. i

In my copending application Serial No. 163,862 filed September 14, 1937, I haver `disclosed a counterbalance of the same type as the counterbalance disclosed in the application of Robert Grifiin De La-Mater referred to, which provides several additional advantageous features. For example my co-pending application discloses means operable after the receiver has been charged with air under pressure for maintaining.

a partial vacuum in the cylinder above the plunger to thus provide increased diiferential pressures on opposite sides of the plunger without increasing the pressure of the fluids in the receiver above the pressure of the atmosphere. ni-sms of my copending application and-the applicationof -Robert Grifiin De La Mater'are similar in theory of operation and practicability. l

I have found that in certain locations in which mechanisms of this character are employed, the temperature changes throughout each twentyfour hours are sulciently small so as to cause .negligible changes in pressures in the receiver in- In such cident `to expansion and contraction. locations, it is not nearly sorv important to provide 'automatic means for guarding against pressure changes incident to temperature variations, and

'I'he mechameans obviously reduces the cost of manufacturev of the apparatus and reduces installation and` maintenance costs.

Accordingly an important object of the present Ainvention is to provide a novel hydropneumatic counterbalance operating on the same principles as the counterbalances of the copendlnig applications referred to wherein pressure conditions within the receiver are maintained within relatively narrow limits, except for temperature variations, without the use of automatic means asso;

ciated with the oil pump, as disclosed in the copending applications referred to.

A further object is to provide a hydropneumauc' counterbalance particularly adapted for use in locations where temperaturer conditions vary be-' tween relatively close minimum and maximum temperatures, and wherein gradual leakage of oil past the counterbalance plunger is compensated for to maintain pressures in the receiver within relatively narrow limits.

A further object is to provide means for preventing` the loss of oil or other non-compressible uid from the system whereby thelevei of the oil in the reservoir may be employed as 'the controlling factor in determining the supplying of oil to the receiver to maintain a constant quantity of oil therein and thus maintain the desired pressures in the receiver between relatively close limits.

A further object is-to provide means for returning to the'reservoir any oil which leaks past the counterbalance plunger to prevent any loss of oil from the system, and to provide means controlled by the level of the oil in the reservoir for determining the effectiveness of the oil pump for supplying oil to the receiver whereby a constant `quantity of oil may be maintained therein.

A further object is to provide a mechanism of the character referred to wherein the inlet pipe of the ,oil pump -is'connected to the receiver below the normal level of the oil therein, and to provide float controlled means for such pipe to admit oil to the pump to be injected into the receiver when y the level of the oil in the reservoir rises above a predetermined 'point incident to the returning thereto of oil leaking past the counterbalance plunger, and to cut 01T the supply of -oil to the to.v

pump when the level of the oil in the reservoir is l at or below such predetermined point.

A further object is to provide a direct connection .between the top portion'of the'cylinder andl the reservoirgfor -returning to the latter oil whichr leaks past the plunger, and to provide means above the packing gland through which the plunger rodreciprocates lat the top of the cylinder for collecting any oil which is wiped from the plunger rod upon each downward stroke thereof.

. to return such oil to the reservoir, `thereby preventing any loss of oil from the system and ren-l dering it practicable to determine the eiTectiveness of the pump for supplying oil to the receiver in accordance with the level of theoil in the reservoir. Y

Other objects and advantages of the invention will become apparent during the course of the following description.

In the drawing I have shown one embodiment of the invention. In this showing: Figure 1 is a side elevation of a standard well rig showing the invention connected thereto,

os A

Figure 2 is a schematic sectionalview of the counterbalance system as a whole, parts being shown in elevation, and,

Figure 3 is an enlarged detail sectional view of the upper end of the cylinder showing the oil collecting means associated with the packing gland.

Referring to Figure 1 the numeral. Illv designates a conventional walking beam mounted as at I to oscillate upon the upper end of a conventional Samson post I2. The walking beam is oscillated in the usual manner by a pitman I3 driven by a crank I4 mounted upon a crank shaft |5 to be driven by the usual prime mover, not shown. The Well end of the beam is connected by the usual polished rod carrier I6 and the usual pump or polished rods I1. A conventional apparatus of this character is provided with headache posts to prevent damage to the apparatus and injury to workmen in the event of breakage of any part of the apparatus. The present construction, as is true of the structures of the co-pending applications referred to, functions to permit the elimination of the usual headache posts by limiting swinging movement of the Walking beam I0.

For the purpose of illustration, the present invention has been shown asl applied to a conventional type of pumping rig. It will be apparent, however, that it is capable of application to any analogous structure.

The present invention comprises a counterbal ance unit indicated as a whole by the numeral I8, comprising a receiver I9 having upper and lowerheads 20 and 2| preferably welded to the body of the receiver. A supporting member 22 is preferably Welded to the lower head 2| and is pivoted as at 23 to a suitable support 24 mounted on the foundation 25 of the pumping rig.

The head 20 is provided with an axial opening 26 surrounded by a relatively heavy ange 21 welded in position on the head concentric with the opening 26. A cylinder 28 projects downwardly through the opening 26. into the receiver and is provided adjacent its upper end with an annular enlarged portion 29 tting within the flange 21. the cylinder being provided above theportion 29 with an outstanding annular flange 30 bolted as at 3| to the flange 21. A bearing 32 is mounted in the upper end of the cylinder and is provided with a suitable bushing 33. The bearing 32 is provided at its upper end with an outstanding annularfiange 34 seating upon the upper end ofthe cylinder and bolted thereto as at 35." The bearing 32 is provided intermediate its ends with a clearancespace 36 communicating at its lower end through grooves 31 with the interior of the cylinder, the bearing 32 otherwise being in tight fitting engagement with the upper end of the cylinder 28.

As more clearly shown in Figure 3, packing means is provided tominimize as completely as possible any leakage of oil past the bushing 33. AV plate 381s bolted as at 39 to the upper end of the bearing 32 and seats against a packing ring 40 surrounding a plunger rod 4I which reciprocates in the bushing 33, the plunger rod being pivotally connected at its upper end to the walking beam as `at 4| and being provided at its lower end with a plunger 42 reciprocating in the cylinder 28. The packing ring 46 engages compressible packing 43 surrounding the plunger drilled as at l5 to provide a passage communicat ing with the space d6. The upper face of the plate 39 is provided with a conical recess 46, and drainage openings il communicate between the recess 46 and the space fit. Accordingly oil wiped from the plunger rod upon downward movement thereof will collect in the recess 46 to be drained through the openings 41 into the space 44, from which the oil is drained through the radial opening 45 for a purpose to be described.

The receiver is adapted to contain a body of oil or other non-compressible fluid as indicated by the numeral 48, the space 49 above the oil being charged with air or other compressible gas under pressure. Plugs 50 are tapped into the wall of the receiver as shown in Figure 2 to facilitate the charging of the receiver with oil and for determining the level of the oil therein, the oil level preferably being determined when the plunger 42 is at its lower limit of movement.

For the purpose of maintaining the proper volume of oil in the receiver a pump is adapted to operate at all times during the operation of the walking beam, although it will become apparent that any other suitable type of pumping means may be employed. The pump is indicated as a whole by the numeral 5| and comprises a cylinder 52 in which is arranged a plunger 53. The cylinder 52 may be maintained stationary in a manner to be described while the plunger 53 is preferably pivotally connected as at 54 to the receiver I9 to be operated by the horizontal component of movement of the receiver incident to swinging movement of the walking beam I6. The opening in. which the pivot pin 54 is arranged may have sufficient play therein to compensate for the very slight vertical component of movement existing between the adjacent portion of the receiver and the plunger 53.

Oil is supplied to the pump 5| from a reservoir 58 which is vented to theatmosphere as at 59.

The level of the oil in the reservoir may be asl indicated by the line 60. A pipe 6I is`connected between the bottom of the reservoir and the cylinder 52 and is provided with a suitable check valve 63 to permit the flow of oil into the pump and to prevent the oil fromilowing from the pump to the reservoir as will be understood. A suitable stationary support 64 is provided for the reservoir 58, and also may be employed for rigidly supporting the pump cylinder 52.

The pipe 6| extends through the bottom of the reservoir to communicate with an outlet pipe 65 the upper end of which is adapted to be closed by a valve 66 carried by an arm 61 pivotally connected as at 6B.to an arm 69 carried by the pipe 65, the free end of the arm 69 being provided with a float 10. It will be apparent that when the level 60 of the oil in the reservoir raises above the point indicated, the doat 10 will open the valve 60 and admit oil to the pump. When the level of the oil in the reservoir is as low as the point 60 the supply of oil to the pump will be cut olf and the pump will be rendered ineffective for supplying oil to the receiver. When Vthe pump is functioning incident to the opening of the valve 66 it will pump oil through a iiexible outlet pipe A1| and thence through a rigid pipe 12 to the bottom of the receiver, the pipe 12 being provided with a check valve I3 functioning as a 'part of the pump to permit oil to flow only in one direction, namely, from the pump to the receiver. A pressure gage I4 is preferably connected in the pipe 12 between the valve 13 and vthe receiver.

Referring to Figure 2, the numeral 15 designates a pipeconnected at one end to the top of the reservoir 58 and at its opposite end to one end of'a flexible pipe connection 18, the other end of this connection leading to a pipe` 11 tapped into the opening 45. A check valve; 18 is arranged in the pipe 11 and permits the flow of fluid therethrough only from the space 36 toward the reservoir 58.l Al three-way valve 19l is arranged between the valve 18 and the passage 45 and is normally arranged in a position to provide communication straight through the pipe 11. However, the three-way valve, under conditions to be described, may be moved to a secv ond position disconnecting the passage 45 from' the valve 18 and connecting it t0 a check valve 80 leading to the atmosphere and operative for adf mltting air into the passage 45. A pipe 8| is connected between the passage 45.and the pipe 11 outwardlyof the check valve 18.

The cylinder is provided with a second radial passage 82, extending through the flange 30, as'shown in Figure 2, and a pipe 83 is connected between the passage 82 and the receiver I9 adjacent the top thereof. Two check valves 84 and 85 are arranged in the pipe 83. These check valves function to prevent the escape of pressure from the top of the receiver during the normal operation of the apparatus. While one check valve is suflicient for the operation of the apparatus, it is preferred that two be employed in order to completely eliminate any escape of air from the top of the receiver.

The operation of the apparatus is as follows:

When the operation of the apparatus is to be started, oil may be supplied to the receiver to the desired level in accordance with the preferred counterbalancing action to be provided in a given installation. For example, with the plunger 42 in its lower. position, oil may be filled to the level of the lower plug 50, whereupon this plug maybe replaced. Oil islikewise supplied to the reservoir 58 t'o the level indicated by the line 60, that is, to the highest depth at which the valve 66 will remain closed. In other words, the oil in the receiver having been placed at the desired level, the level of the oil in the reservoir is at such point that any elevation in such level will result in supplying additional oil to the receiver, as will become apparent. i

With the system charged with oil in the manner stated, the three-way valve 19 is turned to the position in which the passage 45 communicates with the check valve 88, which is inwardlyopening as previously stated.

The operation of the prime mover is now initiated to oscillate the walking beam. Upon each downward movement of the plunger 42, air will be drawn into the upper end of the cylinder 28 through the check valve 80, three-way valve 19 and passage 45. Upon each upward movementof the plunger 42, air in the upper end of the cylinder will be compressed and discharged through the pipe 83 to the air space 49 in the receiver. This operation is continued until the air space 49 is charged with compressible fluid at the desired pressure. The three-way valve 19 is then moved to its other position disconnecting the passage 45 from the check valve 88 and connecting it to the check valve 18, which opens outwardly with respect to the passage 45.

When the full desired pressure in the receiver is attained in the manner described, the system becomes fully1 operative as a counterbalance.

Upon each downward stroke of the plunger 42,

the cil or other non-compressible fluid will be creases progressively upon the progressive downy displaced from the lower end of the cylinder 28 ward movement of the pump rods and'reaches its maximum pressure when the pump rods reach their lowermost position. Thus `it will be apparent that energy is stored in the body of the trapped compressed fluid in the space 49, which energy is expended on the up-stroke of the pump rods to assume part of the load of the pump rods andthe oil Abeing lifted from the well. Thus the prime'mover is required to'perform only a portion of the work incident tothe elevation of the pump. rods. As previously stated, the counterbalance preferably exerts an upward force equal to the'weight ofl the pump rods plus half the weight of the column of oil being lifted, and at least at the beginning of the up-stroke therefore, the force exerted Iby the primemover is the force necessary to elevate half the weight of the column of oil being lifted. Thus it will be apparentthat in accordance with the disclosures of the copending applications referred to, the present construction provides a highly eilcient counter-balancing action, the force required to compress the fluid yin the space 49 stroke of the pump rods being greater than the weight of the pump rods, thus requiring that the prime nover exertfsubstantial force in moving the pump rods to their lower position. The work performed by the prime mover is approximately equal to the work performed by the primey mover during the up-stroke of the pump rods, thus rendering far more uniform the power demands which are made on the prime mover throughout each complete cycle of operation.

It will be apparent that the present construction adds nothing tok the weight of the walking beam and thus permits the use of a much lighter walking beam than is possible in installations wherein counterweighting vis connected to the walking beam itself. Moreover, the counterbalance applies the counterbalancing force at a point closeto the point at which the work is performed, thus being highly advantageous over the use of crank counterbalances. Thev apparatus possesses a greater degree of flexibility than crankcounterbalances, as will be explained, vand the down-stroke of the plunger is limited whereby the device, upon the breakage of the pitman, performs the function of the usualr headache post.

As stated a'love, the counterbalance is highly flexible in its operation and,y any desiredcounterbalancing action may be provided. For example, by using relatively-small amounts of oil in the receiver i9, the difference between minimum and maximum pressures may be made as small as desired. On the'other hand, far greater differences in minimum andmaximum pressures may be provided by increasing the amount ofk oil in the counterbalance. l It also will be apparent that the desired minimum and maximum pressures will be predetermined by the extent to which the space 49 is charged with air upon the initial operation of the apparatus, it merely being necessary to hold the valve 19r in the charging position until the desired pressure in the receiver isreached. y

The present apparatus is particularly'intended for localities in which there is no great change in temperature conditions throughout each twenty-four hour period. under which conditions pressure changes in the receiver incident to expansion and contraction will be minimized. For example, in some localities temperatures are so nearly constant that there will -be not more than lb. variation in pressure in the receiver above and below the theoretically correct pressure. Therefore, the present apparatus is intended to be employed where it is not necessary vto automatically compensate for pressure changes in the receiver incident to changing temperature ,conditions, and accordingly the automatic pressure charging means of the copending applications referred to is eliminated.

However, while leakage of compressible fluid from the receiver is prevented, there will be a slow or continued leakage of oil past the plunger 42 and past the bushing 33 and if such leakage is permitted to continue over substantial periods of time it necessarily follows that there will be progressive lowering of the pressures in the receiver. The present apparatus is Particularly intended to prevent the occurrence of drops in -pressure in the receiver incident to the leakage of oil in the manner stated.

It will be noted that the space 36 surrounding the bearing 32 extends above the passage 45, and accordingly the upwardly extending portion of the space 33 forms a compression space to prevvent the upper end of the cylinderifrom becoming completely filled with the non-compressible fluid, thus resulting in the inevitable breakage of the apparatus.

As oil leaks past the plunger 42, it gradually collects on the upper face of the plunger and when the level of the oil above the plunger moves upwardly as far as the passage 45 upon each upstroke of the plunger, the latter element acts as a pump to discharge the oil through the passage 45, pipe 11, check valve I3 and pipes 16 and 15 to return the oil to the reservoir. Of course, a film of oil will be maintained on the plunger rod 4I to lubricate the bearing rbushing 33, and upon each Vdown-stroke of the plunger rod, a small quantity of the oil will be wiped from the plunger rod 'by the inner edge of the plate 38. The wiped oil will collect in the recess 46 and will drain through the openings 41 into the recess 44, from which it will be discharged by gravity through the pipe 3l to be returned to the reservoir.

Thus it will lbe apparent that while a small quantity of oil will necessarily constantly leak past the plunger 42, none of this oil is lost but all of it is returned to the reservoir. The returning of `such oil to the reservoir gradually raises the level of the oil therein, and when the oil ,level in the reservoir raises slightly above the point 60, the oat will unseat sufliciently to permit the drainage of some of the oil from the reservoir into the pump inlet pipe 6 I.

It will be apparent that the walking beam oscillates about its pivot `II and since the pivot 4I', through which the plunger rod 4| is reciprocated, swings on an arc of a circle concentric with the pivot mounting Il of the walking beam, the receiver will have a small horizontal component of movement during oscillation of the walking beam. Such horizontal' movement is employed for constantly reciprocatingv the pump `plunger 53 as long as the walking beam oscillates. Whenever the valve 66 is unseated incident to the raising of the level of the oil in the reservoir in the manner desired, oil will flow through the pipe 6l into the pump cylinder 52 and will be discharged through pipes 1I and 12 into the receiver. The amount of oil which will be supplied to the pump is always exactly equal to the amount of oil which has leaked past the plunger and accordingly a constant quantity of oil will be maintained in the receiver.

The foregoing functions form the most important features of the present invention. While the level of the oil in the receiver changes constantly during the operation of the walking beam, incident to reciprocation of the plunger 42, the parts described function to maintain a constant quantity of oil in the receiver. Since leakage of air from the space 49 cannot occur, and since the leakage of oil from the receiver is exactly compensated for, it will be apparent that the apparatus will operate constantly between the desired predetermined minimum and maximum pressures for which the apparatus has been set.

If for any reason it is desired to increase the amount of oil in the receiver to step up the initially created pressures therein, additional oil may be supplied to the receiver, whereupon the raising of the level of the oil in the reservoir will result in the unseating of the valve 66. Ac-

cordingly a quantity of oil exactly equaling the amount added to the reservoir will be pumped to the receiver to increase pressures therein. If it is desired to somewhat reduce pressures in the receiver oil may 'be withdrawn in any desired manner from the receiver 53, whereupon the gradual leakage of oil past the plunger 42 will merely reduce pressures in the receiver until the level of the oil in the reservoir is restored to the point indicated by the numeral 60. Thus it will be apparent that the quantity of oil permitted to be ultimately discharged from the receiver Iwill exactly equal the quantity of oil withdrawn from the reservoir.

As previously stated, the present apparatus is particularly intended for use in localities in which no great differences in temperature occur throughout each twenty-four hour period. Thus the apparatus permits the elimination of the relatively expensive blow-off valve shown in each of the prior applications referred to for controlling pressures in the receiver. The present apparatus requires the use of no pressure responsive valves of any type and yet operates to maintain constant pressures in the receiver, such pressures varying solely through differences in temperature conditions in the locality in which the apparatus is employed.

When Ithe apparatus is initially charged with air the valve 19 opens the passage 45 :to the check valve 80, as stated. When the desired pressure in the space 49 is reached, the apparatus is prefenably stopped with the plunger 42 at its upper limit of movement, whereupon the valve 19 is turned to i-ts normal position closing communication between .the passage 49 and the check valve 80. Accordingly no further air will be admitted to the upper end of the cylinder, and a partial vacuum will be created upon each downward movement of -the plunger 42. Thus the apparatus permits the utilization of increased differential pressures between the space 49y and the space above the plunger 42, without further increasing .the pressures of Ithe iluids in the receiver above atmospheric pressure. This feature of the apparatus forms no part of the present 'invention per se, but is described and claimed in my copend-ing application referred to.

It is to be understood that .the form of the invention herewith shown and described is to be .taken as a preferred example of .the same and that various changes in the shape, size andarrangementqof parts may be resorted to without departing from the spirit of the invention or vthe scope of the subjoined claims.

1. A counterbalance for parts having uniform relative movement, comprising a compression chamber, Ea hollowmember, a` fluid displacing member movable in said hollow member, said compression chamber Ahaving relatively unrestricted communication with said hollow member, a body of anon-compressible fluid at least partially filling said compression chamber and extending into said hollow member 'to be displaced therefrom by said displacing member, and means for replenishing the non-compressible fluid in accordance with the leakage of such fluid from the counterbalance. l

2. A counterbalance for parts having uniform relative movement, comprising a compression chamber, a hollow member, a fluid displacing member movable in said hollow member, said compression chamber having relatively unrestricted communication with said hollow member, a body of a non-compressible fluid at least partially filling said compression chamber and extending into said hollow member to be displaced therefrom by said displacing member, means for collecting non-compressible fluid leaking from the counterbalance, and means for replenishing the non-compressible fluid in accordance with the collection of such uid by said last named means.

3. A counterbalance comprising a compression chamber, a hollow member, a fluid displacing member movable in said hollow member and operable from a point externally of said compression chamber and said hollow member, said compression chamber 'communica-ting with said hollow member, a body of a non-compressible uid at least partially filling said compression chamber and extending intosaid hollow member to be displaced therefrom by said Adisplacing member, a receptacle, means for transferring to said receptacle non-compressible fluid leaking from said hollow member, and means controlled by the level of .the non-compresslble fluid in said receptacle for supplying to said compression chamber noncompressible fluid in amounts equal rto the amounts of the leakage of such fluid from said hollow member.

4. A counterbalance comprising a compression chamber, a hollow member, a fluid displacing member movable in said hollow member and operable from a point externally of said compression chamber and said hollow member, said compression chamber communicating with said hollow member, a body of a non-compressible uid at least partially filling said compression chamber and extending into said hollow member to be displaced .therefrom by said displacing member, a receptacle containing a body of a non-compressible fluid to a predetermined level, a pump hav- -ing its inlet connected to said receptacle and its outlet connected to said compression chambena float in said receptacle closing said inletA when the level of -the non-compressible fluid in such receptacle is at or below said predetermined level and operable for admitting non-compressible fluid to said inlet when .the fluid raises above said predetermined level, and means for returning to said receptacle non-compressible fluid leaking from said hollow member.

5. A counterbalance for parts having uniform relative movement, comprising a compression chamber, a cylinder having substantially unrestricted communication at its lower end With-said f compression chamber, a plunger reciprocable in said cylinder and projecting from the upper end thereof, a body of a non-compressible uid at least partially filling said compression chamber Y and displaceable from the lower end of said cylinder upon "downward movementl of said plunger,

and means for replenishing the non-compressible fluid in accordance with .the leakage of such uid from the counterbalance.

6. A counterbalance for parts having uniform rela-tive ymovement comprising a compression chamber, a cylinder having substantially unrestricted communication at its lower end ywith said compression chamber, a plunger reciprocable in said cylinder and projecting from the upper end 1 thereof, a body of a non-compressible fluid' at least partially filling said compression chamber and displaceable from the lower end `of' said cylinder upon downward movement of saidplunger, and means for supplying non-compressible fluid to said compression chamber, said means being operable in accordance with the amounts of noncompressble uid leaking past said plunger.

7. A' counterbalance comprising a compression chamber, 'a cylinder communicating at its lower end `with said compression chamber, a plunger reciprocable in said cylinder and projecting from the upper end thereof, a body of a non-compressible fluid at least partially filling said compression chamber and displaceable from the lower amount of non-compressible fluid to said como pression chamber. v

8. A counterbalance comprising a compression chamber, a cylinder communicating at itsv lower end with saidy compression chamber, a plunger reciprocable in said cylinder and projecting from the upper end thereof, a body of a non-compressible fluid at least partially lling said compression chamber and displaceable from the lower end of said cylinder upon downward movement of said plunger, a receptacle containing a body of a non-compressible fluid, means for collecting non-compressible fluid leaking past said plunger and returning i-t to said receptacle, and means' for transferring non-compressible fluid from saidvreceptacle to said body of' noncompressible fluid, said last named means being controlled in accordance with the amounts 'of leakage fluid returned to said receptacle.

9. A counterbalance comprising a compression chamber, a cylinder communicating at its lower end with said compression chamber, a plunger reciprocable in said cylinder and projecting from the upper end thereof, a body of a non-compressible fluid at least partially filling said compression chamber and displaceable from the lower end of said cylinder upon downward movement of said plunger, a receptacle containing a body of a non-compressible uid, means for collecting non-compressible fluid leaking past said plunger and returning it to said receptacle, a pump having its inlet connected to said receptacle and its outlet to said compression chamber, and means for admitting non-compressible fluid from said receptacle to said pump in accordance withy the amounts of leakage fluid returned to said receptacle.

10. A counterbalance comprising a compression chamber, a cylinder communicating at its lower end with said compression. chamber. a plunger reciprocable ,in said cylinder and projecting from the upper end thereof, a body of a non-'compressible fluid at least partially filling saidcompression chamber and displaceable from the lower end of said cylinder 1111011 downward movement voff said plunger.. a vreceptacle containing a body of a non-compressible fluid to a predetermined level, a pump vhaving its inlet connected to said receptacle and its `outlet kconnected to said compression chamber, a float having a valve connected therewi-th closing said inlet when the level vof the non-compressible fluid in said receptacle vis Vat or below said predetermined level, said float being operable for opening said valve to admit fluid to said pump when the non-compressible uid in said receptacle rises abovesaid predetermined level, and means for returning to saidvreceptacle non-compressible fluid leaking from said cylinder.

1l. A counterbalance comprising a compression chamber closed to the atmosphere and containing compressible fluid under pressure, a cylinder having its lower end communicating with said compression chamber, a plunger reciprocable in said cylinder, a body of a non-compressible fluid in said compression chamber displaceable fromfsaid cylinder upon downward movement oi' said plunger, the amount of said noncompressible fluid being sufficient to form a seall leaking past said plunger, a bearing in the upper end of saidv cylinder in which said plunger reciprocates, means for returning to said receptacle non-compressible fluid collecting on said bearing from said plunger, and means for supplying from said receptacle to said compression chamber non-compressible uid in amounts equal to the amounts of non-compressible fluid returned to saidvreceptacle,

12. A counterbalance comprising a compression chamber closed to the atmosphere and containing compressible fluid under pressure, a cyl,-

inder having its lower end communicating withv said compression chamber, a-plunger reciprocable in said cylinder, a body of a non-compressible fluid in said compression chamber displaceable from said cylinder upon downward movement of said plunger, the lamount of said non-compressible fluid being sufficient to form a seal between said compressible fluid andthe lower end of said cylinder, a receptacle containing non-compressible fluid to a predetermined level, means for returning from the upper end of said cylinder to said receptacle non-compressible fluid leaking past said plunger, a bearing in the upper end of said cylinder in which said plunger reciprocates, means for returning to said receptacle non-compressiblejfluid collecting on said bearing from said plunger, a pump con-V nected between said receptacle and said` compression chamber, and means for controlling said pump to render it effective for transferring from said receptacle to said compressionchamber noncompressible fluid in amountsj equal to the amounts lof'non-compressible fluid returned to said receptacle. v

13.' Ay counterbalance comprising `a compression chamber closed to the atmosphere and containing compressible fluid under pressure, a cylinder vhaving its lower end communicating with said compression chamber, a plunger reciprocable in said cylinder, a body of a non-compressible fluid in said compression chamber displaceable from said cylinder upon downward movement of said plunger, the amountof said noncompressible fluid being sufficient to .form a seal between said compressible fluid and the lower end of said cylinder, a receptacle con-taining noncompressible fluid to a predetermined level, means for returning from the upper end of said cylinder to said receptacle non-compressible fluid leaking past said plunger, a bearing'in the upper end of said cylinder in which said plunger reciprocates, means for returning to said lreceptacle non-compressible fluid collecting on said bearing from said plunger, a pump connected between said receptacle and said compression chamber, and means including a float in saidl receptacle controlled by the level of the noncompressible fluid therein for rendering said pump effective for transferring from said receptacleto said compression chamber non-compressible uid in amounts equal to the amounts of non-compressible fluid returned to said receptacle.

14. A counterbalance comprising a compression chamber closed to theatmosphere and containing compressible fluid under pressure, a cylinder having its lower end communicating with said compression chamber, a plunger reciprocable in said cylinder, a body of a non-compressible fluid in said compression chamber displaceable from said cylinder upon downward movement of said plunger,` the amount of `said non-compressible fluid being suillcient to form a seal between said compressible fluid andthe lower end oi' said cylinder, a receptacle containing non-compressible fiuid to a predetermined level, means for returning from the upper end of said cylinder to said receptacle non-compressible fluid leaking past said plunger, a bearing inthe upper end of'` said cylinder in which said plunger reciprocates. means for returning to said receptacle noncompressible fluid collecting on said bearing from said plunger, a pump having its inlet connected to said 4receptacle and its outlet to said compression chamber, a valve in said receptacle controlling said inlet, and a float in said receptacle controlling said valve to admit non-compressible fluid from said receptacle to said pump to be injected into said compression chamber when the level lof? .the non-compressible fluid in 15. A counterbalance comprising a compression chamber, a substantially vertical cylinderv communicating at itslower end with said compression chamber, a plunger reciprocable in said cylinder and having a. plunger rod projecting from the upperl end thereofla bearing in the upper y end of said cylinder surroundingl said plunger .necting said cylinder above the upper limit of movement of said plunger to said receptacle to return to the latter non-compressible fluid leak- `ing past said plunger, means for collecting noncompressible fluid from said plunger rod above said bearing and returning it to said receptacle. and means for transferring from said receptacle tosaid .compression chamber non-compressible iluidin amounts equal to the amounts of noncompressible/fluid returned to said receptacle by said conduit and by saidcollecting means.

16.v A counterbalance comprising a compression chamber, a substantially vertical cylinder communicating at its lower end with said compression chamber, a plunger reciprocable in' said cylinder and having a plunger rod projecting from the upper end thereof, a bearing in theupperendfof said cylinder surrounding said plung-` er rod, .a body of a non-compressible uid in said compression chamber, said compression chamber containing compressible iluid under pressure adapted to be compressed by said non-compressible fluid-upon displacement thereof from the lower end of said cylinder when said plunger moves downwardly, a receptacle, a conduit connecting said cylinder above the upper limit of movement of said plunger to said receptacle to return to the latter non-compressible fluid leaking past said plunger, means for collecting noncompressible fluid from -said plunger rod'above said bearing and returning it to said receptacle, and means for transferring from said receptacle to said compression vchamber non-compressible v fluid in amounts equal to the amounts of noncompressible fluid returned to said receptacle by said conduit and by said collecting means, said last named means comprising a pump having its inlet connected'to said receptacle and its outlet connected to said compression chamber, and float controlled means in said receptacle `for determining the admission of non-compressible fluid from said receptacle to said pump'in accordance with the rate of `return ci' non-compressible fluid to said receptacle by said conduit and by said collecting means.` l

17. A counterbalance comprising a compression chamber closed to the atmosphere, a substantially vertical cylinder communicating at its lower` end with said compression chamber, a plunger reciprocable in said cylinder and having an upwardly'extending plungerA rod, abearing mounted inthe upperv end ofy said cylinder and surrounding said plunger rod, said compression chamber containing a body of a non-compressible fluid in.` the bottom thereof and being charged above said non-compressible fluid with compressible uid under pressure, said non-compressible fluid being displaceable from thelower end of said cylinder upon downward movement of said plunger to compress said compressible fluid, areceptacle containing non-compressible fluid to a predetermined level,'a conduit affording communication-between said receptacle and said cylinder above said plunger when vthe latl ter is at its upper limit of movement to return to said receptacle .non-compressible fluid leaking past said plunger, the upper face of said bearing being. provided with a recess surrounding said plunger rod to receive therefrom non-compressible fluid leaking past said'bearing, a conduit for returning non-compressible fluid -fromsaid recess to said receptacle, and means for transferring from` said receptacle to said compression chamber non-compressible fluid in amountsequal to the amounts of non-compressiblev fluid 'returned to said receptacle by said conduits.

18. A counterbalance comprising va compression chamber closed to the atmosphere, a substantially vertical cylinder communicating at its lower end with said compression chamber, a plunger reciprocable in'said cylinder and having an up wardlyextending plunger rod,1a ybearing mounted in the upper end of said cylinder land, surrounding said plunger rod, said compression chamber containing a bodyofa non-compressible fluid in the bottom ythereof .andbein'g charged 'above said non-compressible fluid with compressible fluid under pressure, said non-compressible fluid being displaceable from the lower end of said cylinder upon downward movement of said plunger` to compressl saidl compressible fluid, a receptacle containing"filon-compressible fluid to a predetermined level,a conduitaii'ordt ing communication lbetweenjsaidy receptacle and sald cylinder above said plunger'when the latter is at its upper limit of movement to return to said receptacle non-compressible fluid leaking past said plunger, the upper face'oi' saidbearing being provided with a recess surrounding said plunger rod' to receive therefromfnoncompres sible duid leaking pastsaid bearing,V a conduit for returning non-compressible uidfromsaid recess to said receptacle, and means'fo'r transferring from said receptacle'to 'saldcompression chamber non-compressible fluid in amounts 25 equal to the amounts of non-compressible. fluid returned to said receptacle by said conduits, said last named' means comprising a ,pumpv having its inlet connected to said receptacleand lts outlet connectedl to said compression chamber, and float controlled means for admitting to said inlet oil collecting in said receptacle above said predetermined level. .i y.

19. A counterbalance for parts having uniform, relative movement, comprising a compression. chamber, a hollow member, a fluid displacing. member movable insaid hollowmember, said compression chamber having relatively unrestricted communication with l n ber, a body of a non-compressible fluid at least 'partially filling said compression' chamberfand. extending into said hollow member to be displaced therefrom by saidmdisplacing .'member,

said hollow v memmeans for supplying non-compressible fluidI to..

ance with the leakage of non-compressible vfluid from the counterbalance.

20. A counterbalance'for parts having uniform, relative movement,` comprising .a compression chamber, a hollow member movable in said compression. chamber` having relativelyy unref a stricted communication with said hollowfmember, a`, body of a non-compressible -fluid at least member.'a fluid displacing hollow member, said.

partially filling said compression` chamber and extending into said hollow member to .be displaced therefrom by said displacing member, and

means for collecting non-compressible fluid leak'-` ing fromthe counterbalancethe counterbalance having means for vreturning non-compressible. fluid from said last named ofy non-compressible fluid.

means to said body 21. A counterbalance fora member having uni-v form relative movement, comprising a 'pair of.

structures one'of which is 'connected to said mem-4 ber andthe other of which is connectedto .a stationary support, one of saidv members com"-l prising a cylinderl and the other comprising a plunger reciprocable in said cylinder and operative for displacing fluid therefrom upon move'- ment of said member in one direction', the coun- A terbalance having a compression chamber. into which fluid is displaced `from said cylinder by said plunger, the counterbalance containing a 'illling said compression chamber and sealing a body of a compressible uid therein, and means for replenishing the non-compressible fluid in accordance with the leakage of such fluid from the counterbalance.

22. A counterbalance for a member having uniform relative movement, comprising a pair of structures one of which is connected to said member and the other of which is connected to a stationary support, one of said members comprising a cylinder and the other comprising a plunger reciprocable in said cylinder and operative for displacing iiuid therefrom upon movement of said member in one direction, one of said structures having 'a compression chamber into which'tluid is displaced from said cylinder by said plungerI the counterbalance containing a body of a non-compressible iiuid atleast partially filling said compression chamber and sealing a body of a compressible fluid therein, and means for replenishing the non-compressible fluid in accordance with the leakage of such fluid from the counterbalance.

23. A counterbalance for parts having uniform relative movement, comprising a compression chamber, a hollow member, a fluid displacing member movable in said hollow member, said compression chamber having relatively unrestricted communication with said hollow mem-v ber, a body of a non-compressible fluid at least partially illling said compression chamber and extending into said hollow member to be displaced therefrom by said displacing member, and means automatically controlled in accordance with the amounts of leakage of non-compressible fluid, from the counterbalance for replenishing the non-compressible tluid in the counterbalance. n

.tive for displacing iluid therefrom upon movement of said member in one direction, one of said structures having a compression chamber into which tluid is displaced from said cylinder by said plunger, the counterbalance containing a body of a non-compressible iiuid at least partially lllng said compression chamber and sealing a body of compressible iluid therein, and means automatically controlled in accordance with the amounts of leakage of non-compressible uid from the counterbalance for replenishing the non-compressible iiuid in thecounterbalance.

f HAROLD WILLIAMS RAMEY. 

